Up to 12 former teachers from the world-famous Chetham’s School of Music are being probed by police as their investigation into decades of historic sexual abuse widened significantly today.

All taught as permanent staff or freelance tutors at an institution where pupils claim everyone knew of the abuse but it was ‘brushed aside or suppressed’ for decades.

It is understood that some of those alleged to have carried out sex attacks are still teaching music to youngsters in other locations.

Detectives have also begun interviewing alleged victims, believed to number more than ten and living both in Britain and abroad.

Spark: It was the conviction of choirmaster Michael Brewer (right), which led to the tragic death of victim Frances Andrade (left), and now up to 12 former staff being probed by police

Cover-up? Detectives have received more than 20 complaints about historic sexual abuse at Chetham's, pictured

Nearly all of the abuse is alleged to have taken place at Chetham’s - however it is believed some took place when complainants were pupils at the Royal Northern College of Music, also in Manchester.

The allegations came to light after the trial of former Chetham’s choirmaster Michael Brewer, convicted earlier this year of indecent assault in the 1970s and 1980s.

His victim, Frances Andrade, killed herself after giving evidence against him at Manchester Crown Court.

A second music teacher, Wen Zhou Li, a
57-year-old violin tutor from Cheshire who has worked at both Chetham’s
and the RNCM, has also been arrested on suspicion of rape before being
released on bail. No charges have been brought and Mr Li strenuously
denies the allegations.

Paul Lewis, an acclaimed pianist who studied at Chetham’s in the 1980s, claimed ‘every pupil’ knew of the abuse.

Former teacher Malcolm Layfield was accused by Frances Andrade
of preying on students. A former pupil has said there was a 'cover-up'

Malcolm
Layfield, who was head of strings at the Royal Northern College of
Music, was accused by Frances Andrade of preying on students.

He said he had resigned from the Manchester-based college as his position was ‘untenable’.

Married
Mr Layfield, 61, taught at Chetham’s alongside Brewer. He has admitted
sexual relationships with at least six pupils, some of whom were just
16.

It was stated all the girls were over the age of consent and the ‘liaisons’ were ‘consensual’.

The
news comes as more than 1,000 former Chetham’s pupils and professional
musicians signed a petition calling for an independent inquiry into
sexual abuse at the school and other private music conservatoires.

The petition’s organiser, former
Chetham’s pupil and professional pianist Ian Pace, says he believes the
Brewer trial is just ‘the tip of the iceberg’.

Mr Pace, now based in
London, said: ‘There has been a huge groundswell of support for the
petition from ex-Chetham’s pupils from all areas, including people who
have been there very recently.

‘A
lot of parents have also supported it, along with musicians of all
different types, plus people working in education and other musical
organisations.

‘The number of people contacting me to talk about these issues is also significant.

‘These
are problems which have gone unaddressed for too long, like the nature
of teacher-pupil relationships and abuse, whether it’s physical, sexual
or emotional, which causes long-term damage.

‘Unfortunately I think what came out at the Michael Brewer trial is just the tip of the iceberg.’

A spokeswoman for the RNCM declined to comment as did Greater Manchester Police. MailOnline approached Chetham's for comment, but they are yet to respond.